Wpf performance issue on vdi

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C#

WPF

I've added a fairly simple control to an existing WPF application. The control launches in its own window and uses a combo box to allow the user to build up an editable list. As selections are added to the list, they appear in the list accompanied by a delete button. The XAML for the list is:

<StackPanel Grid.Row="2">
            <ItemsControl  Name="icSelected"  ItemsSource="{Binding Path=SelectedUsers, RelativeSource={RelativeSource FindAncestor, AncestorType=my:Recipients, AncestorLevel=1}}">
                <ItemsControl.ItemTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal">
                            <Label Name="lblRecipient" Content="{Binding Path=DisplayName}" Width="150"/>
                            <Button Name="btnRemove" HorizontalAlignment="Right" Click="btnRemove_Click">
                                <Image Source="Resources/delete.png"/>
                            </Button>
                        </StackPanel>
                    </DataTemplate>
                </ItemsControl.ItemTemplate>
            </ItemsControl>
        </StackPanel>

This was all running perfectly well until I deployed it. Running the deployed version from a VDI session, it takes the best part of a minute for an item to be added to the list. Task Manager shows the window as being unresponsive but doesn't indicate any unusual activity - System Idle remains at around 99%. SQL Profiler confirms that there is no database activity occurring during the delay and Snoop doesn't indicate any unexpected events.

If I run the same binary from my local machine, however, everything is fine.

The application (a monumental pile of junk) otherwise runs equally happily on VDI or a physical machine.

On further investigation, the bottleneck only seems to occur if the button is being used - i.e. if I remove the button altogether, everything runs at a reasonable speed.

What I have tried:

I've tried removing the image from the button and I've tried removing the click event handler but neither has had any effect.

I've tried nullifying style settings, also to no avail.